How to change the checkbox size of QFileSystemModel and custom checkbox shape

[IknowQT]

Declare it as subclassing in a class that inherits from QFileSystemModel and give it a checkbox property.
The result was successful. However, it is a basic check box provided by qt and the size is also too small. I want to grow a checkbox and change it to a checkbox I have defined.

class usrFileSystemModel : public QFileSystemModel
{
	Q_OBJECT


private:
	mutable QMap <qint64, Qt::CheckState> m_CheckedItems;

public:
	usrFileSystemModel(QObject *parent);
	~usrFileSystemModel();


	// [ SubClassing ]
	virtual bool			setData(const QModelIndex& index, const QVariant& value, int role);
	virtual Qt::ItemFlags	flags(const QModelIndex& index) const;
	virtual QVariant		data(const QModelIndex& index, int role)const;

signals:
	void					itemChecked(const QModelIndex&);


protected slots:
	void onItemChecked(const QModelIndex& index);
};



#include "usrFileSystemModel.h"

usrFileSystemModel::usrFileSystemModel(QObject *parent)
	: QFileSystemModel(parent)
{
	this->connect(this, SIGNAL(itemChecked(const QModelIndex&)), SLOT(onItemChecked(const QModelIndex&)));
}

usrFileSystemModel::~usrFileSystemModel()
{
}

bool usrFileSystemModel::setData(const QModelIndex& index, const QVariant& value, int role)
{
    if (role == Qt::CheckStateRole && index.column() == 0) {

        m_CheckedItems[index.internalId()] = static_cast<Qt::CheckState>(value.toInt());
        emit itemChecked(index);
        emit dataChanged(index, index.sibling(0, 0));
        return true;
    }

    return QFileSystemModel::setData(index, value, role);
}

Qt::ItemFlags usrFileSystemModel::flags(const QModelIndex& index) const
{
    return QFileSystemModel::flags(index) | Qt::ItemIsUserCheckable;
}

QVariant usrFileSystemModel::data(const QModelIndex& index, int role) const
{
    if (role == Qt::CheckStateRole && index.column() == 0) 
        return QVariant(m_CheckedItems[index.internalId()]);

    return QFileSystemModel::data(index, role);
}

void usrFileSystemModel::onItemChecked(const QModelIndex& index)
{
    Qt::CheckState state = m_CheckedItems[index.internalId()];
    fetchMore(index);
   
    if (state == Qt::Checked || state == Qt::Unchecked) 
    {
        for (int i = 0; i < rowCount(index); i++) 
        {
            QModelIndex child = index.child(i, 0);
            if (m_CheckedItems[child.internalId()] != state)
                setData(child, state, Qt::CheckStateRole);
        }
    }

    QModelIndex parent = index.parent();
    if (parent.isValid()) 
    {
        state = m_CheckedItems[parent.child(0, 0).internalId()];
        if (state == Qt::PartiallyChecked)
            m_CheckedItems[parent.internalId()] = state;
        else 
        {
            int i = 1;
            while (i < rowCount(parent) && m_CheckedItems[parent.child(i, 0).internalId()] == state)
                i++;
            if (i != rowCount(index))
                state = Qt::PartiallyChecked;

            m_CheckedItems[parent.internalId()] = state;
        }
    }
}